Reggie, a mastiff type dog, was being walked by Sunnie Depass when he spied a Maltese chihuahua off its lead in Limes Avenue off East Heath Road in Hampstead, Highbury Magistrates Court heard on Thursday (October 25).

A 13-year-old scooped up the smaller dog as Reggie approached, but it wriggled free and the mastiff clamped its jaws around the chihuahua and killed it at around 3pm on July 7.

Depass, from Fairbridge Road near the Whittington Hospital, claimed she had been told by its owner Matthew Hayward that Reggie was “as harmless as a six-month old puppy”.

She said: “It was a horrible incident, dreadful.”

Lawyer Phil Saunders, acting on behalf of the City of London Corporation which manages the Heath, said the prosecution was not claiming Depass, 46, was a professional dog walker.

He said: “We have not had a case where a dog has died for some years. We will be writing to Mr Hayward saying the dog is not welcome on the Heath in the future unless it is muzzled. It’s quite a serious case.”

Both Hayward and Depass pleaded guilty to failing to control the dog – a breach of the Heath byelaws. Hayward was fined £765 and Depass was ordered to pay £135.